$\dfrac{3}{8} + \dfrac{9}{10} = {?}$
Answer: ${\dfrac{3}{8}}$ ${\dfrac{9}{10}}$ $+$ ${\dfrac{3 \times 5}{8 \times 5}}$ ${\dfrac{9 \times 4}{10 \times 4}}$ $+$ ${\dfrac{15}{40}}$ ${\dfrac{36}{40}}$ $+$ $ = \dfrac{{15} + {36}}{40} $ $ = \dfrac{51}{40}$